Abstract: The structure and the principles of ultrasonic microscopical detection system were introduced. By applying technology of ultrasonic microscopical detection, materials were detected, and the applicational researches of the device soldering of automotive engines were conducted. Results of the research showed that the technology of ultrasonic microscopical detection could be applied in many fields such as detections of coat material, plastic-packaging integrated circuitry, and the quality of the device soldering of automotive engines. Three scanning images, A, B, and C could be displayed real-timely when detecting, and the results of bug detecting was thus evident.